1. Field of the Invention
The present invention relates to a ski brake of which the braking shoes are retracted to a flush-fitting position so that they do not project from the side edges of the ski.
2. The Prior Art
The most popular ski brakes comprise a pair of pivoting brake arms disposed on either side of the ski and pivoted on top thereof about a transverse axis. These arms are interconnected at one end by a cross member acting as a control pedal, a return spring constantly urging said arms to pivot towards their positions in which their end opposite said one end is lowered with respect to the bottom surface of the ski, so as to penetrate into the underlying snow layer. Ski brakes of this character consist as a rule of metal wire and in this case the transverse pivot means may consist of a pair of elbows formed integrally with the pivot arms, respectively.
When the ski boot is fitted to the ski, it exerts a pressure upon the control pedal, thus maintaining the operative portions of the brake arms in a raised or retracted position. However, in this case the operative portions of said arms project outwards in relation to the ski edges, and under certain circumstances this may prove particularly detrimental.
Therefore, certain ski brakes have been so designed that the operative portions of their pivoting arms are moved towards each other above the ski top when they are in their raised and retracted position. Various means have been proposed for maintaining the pivoting arms in this retracted position.
Thus, the French Patent No. 2,272,695 corresponding to U.S. Pat. No. 3,989,271 issued Nov. 2, 1976 discloses a ski brake in which the brake arms are retracted by tensioning the metal wire constituting said arms, by using stretching means in the form of an overcenter device adapted to be flattened by the ski boot pressure. However, in operation this system is not fully reliable, for a considerable force is required for altering the configuration of the brake arm wire. In fact, the stiffness of this wire must on the other hand be sufficient to provide an efficient braking action and prevent the brake arms from being distorted in case of simple shocks.
In another French Patent No. 2,308,389 (application No. 76 11752) the movement of the brake arms to their raised and retracted position is obtained by exerting a pressure on a deformable plate or hinged quadrilateral disposed under the boot location so as to be flattened by the boot when the latter is fitted in position. The arrangement is such that when flattened this plate or hinged quadrilateral causes the two brake arms to move towards each other after having been raised to their retracted position.
However, if the control plate is a bent blade, the latter will exert an excessive pressure on the boot, and this is likely to interfere with the boot release when the safety ski binding is operated, for instance in case of fall. Besides, if the control plate consists of a hinged quadrilateral, the assembly contemplated appears to be particularly complicated and expensive. Moreover, this system is scarcely reliable because its operation is likely to be impaired in case of icing.
In a further French Patent No. 2,330,419 (application No. 75 34137) the brake arms are retracted by means of one or a plurality of cam faces carried for example by an auxiliary pedal. But also in this case the solutions contemplated are not fully satisfactory. In fact, since the movement of retraction of the brake arms is obtained by altering the shape of the metal wire constituting said arms, a considerable effort must be exerted thereon to this end. Moreover, this system also develops additional stress interfering with the normal release of the ski boot by the ski binding.
On the other hand, to avoid abnormal over-all dimensions, the height of the control cam faces must be limited, and this is attended by a detrimental limitation of the retraction movement of the brake arms.
Finally, in another known proposal the brake arm retraction is obtained by causing the brake arm to pivot in a bearing having its axis disposed in a transverse plane in relation to the ski and inclined with respect to the ski top surface (cf. French Patent No. 2,228,506, FIG. 11, Application No. 73 17074). The main advantage of this system is its extreme simplicity. Yet, it is objectionable in that the slightest change in the brake arm configuration may cause this arm to rub the ski edge and possibly be locked thereby, since the inward and upward movements of the ski arm are combined into a single movement. Another inconvenience of this arrangement lies in the fact that to obtain a sufficient inward or retraction movement the pivot bearing must be located at a relatively high level, a requirement that cannot be met if the brake is disposed under the ski boot.
It is therefore clear that all the various systems proposed up to now for retracting the brake arms of ski brakes have serious drawbacks. Under these conditions, the present invention is directed to provide a ski brake wherein the brake arms are retracted by using particularly simple, reliable and economical means; besides, the system of the present invention is extremely simple to operate and exerts on the boot sole a substantially negligible thrust.